Gun



Fb., 19, 1946. W` T, Gom-0N 2,395,044

GUN

Filed April 2,. 1942 @www Patented Feb. 19, 1946 UNirED STATES GUN Walter T. Gorton, Springfield, Mass. Application April 2, 1942, serial No.1437,3r1

12 Claims.

(Granted under the act o! March 3, 1883, as

amended April 30,

The invention described herein may be manufactured and used by' 0r for the' Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to guns and more particularly to thel barrel thereof. A'gun `barrel Vis subjected tol severe conditionsinnormal operation and the reaction of the interior surfaces of the chamber and bore of the barrel to these conditions is generally the determining'factor of the operating life of the fgun. Both thechamber and the bore of a gun'barrel are subject to corrosion, which is the term generally applied to deterioration of these interior surfaces :by the formation of oxides and chlorides of iron. Such corrosion is caused by the liberation of very active chemicals, particularly oxygen, in the discharge of each cartridge, and takesplace despite careful cleaning. In addition the barrel boreis also subjected to a deteriorating effect known asl erosion. The exact reason for erosion is a subject of many conflicting theories but it is apparently caused by the high velocity washing of the Steel surface by high temperature and high pressure gases developed by the discharge of the cartridge. The effect of corrosion is the pitting and rusting `of the steel surfaces of the chamber and zbarrel. The effect of ,erosion appears as an actual washing away of portions of the bore surface,

The resultant detrimental effects of corrosion and erosion on the performance of a gun are well known. The corrosion of the chamber is particularly detrimental to the operation of a gun of the automatic type. In such type of gun, ease of extraction of the empty cartridge case is a prime factor; however, the roughening of the chamber surface by erosion makes the extraction gradually more difficult until the necessary extracting force exceeds that which the automatic mechanism of the gun can develop. Hence the gun fails to operate. The corrosion and erosion of the bore produces an enlargement of bore diameter thus permitting the gases to blow by the projectile, resulting in a gradually increasing loss of muzzle velocity of the projectile. Furthermore the deterioration of the lands of the riiling causes inaccurate grooves to be cut in the projectile resulting in a loss of accuracy and the malfunction known as key-holing of the bullet.

It has been previously suggested, asin U. S. Patent No'. 1,886,218 to Olin and Schuricht, that corrosion and erosion of the bore of gun barrels might be retarded by the electrolytic deposition of a coating of chromium throughout the entire bore. It is an object of this invention to apply this suggestion in a novel manner to protect the chamber and bore of a gun from corrosion and erosion. It is an object of this invention to lprovide a coating of hard and practically non-corrosive metal to the chamber and the portion of the bore immediately adjacent to the chamber whereby the actual physical configuration of the interior of the bore is changed.

It is a further object of this invention to apply a coating of hard and practically non-corrosive metal to a portion of a gun barrel bore whereby retardation of corrosive and erosive effects is obtained'and at the same time a substantial increase in the muzzle velocity of the projectile is secured. l0 A particular object of this invention is to obtain an Aincrease of muzzle velocity of the projectile :by an electroplated deposit of a hard metal on a portion of the bore.

The "fic nature of the invention as welles other frigiects and advantages thereof will clearly appea' rom a description of a preferred embodiment as shown in theaccompanying drawing in which: c c

Fig. l is a sectional view of a gun barrel embodying this invention.

Fig. 2 is an enlarged sectional view of the chamber end of f in barrel embodying one modification of this invention.

Fig. 3 is also an enlarged sectional view of the chamber end of a gun barrel embodying another modification of this invention.

In Fig. l, there is shown a gun barrel I having a bore portion 2 and a cartridge chamber 3. The

- barrel is ried in any conventional manner, providing it with the lands 4. It has been observed that in a firearm of the automatic type, corrosion of the barrel chamber is a more serious detrimental factor to the performance of a gun than corrosion of the bore, due to the difiiculty of extraction. It has been further observed that practically all serious erosion effects are produced in the vicinity of the barrel chamber and the portion of the bore immediately adjacent to the cham-ber. It follows that if only these por- .10 tions were lprovided with a coating of hard and practically non-corrosive metal, the detrimental effects of corrosion and erosion of gun performancewill be substantially reduced. At the same time the cost of a coating of such limited extentwill be only a fractional part of the cost of a coating extending throughout the bore. A coating 5 of a suitably hard, corrosion resisting metal having good adhering properties is provided cov ering the chamber and the adjacent part of the bore. While chromium has been found to be a particularly desirable coating metal, it is obvious vthat other metals having similar properties may -be utilized for example, nickel. cadmium, or

silver. The thickness of this coating may preferably be only a few ten-thousandths of an inch which is well within the range of standard tolerances permitted today in interior dimensions of the barrel and bore of the gun. It is, therefore, not necessary to provide a gun with a non-standard chamberv or bore dimension or a special diameter cartridgeor projectile. Of course thicker coatings may be applied if the gun dimensions are modied accordingly,

As shown inv Figure 2, in exaggerated non-pro"Y from the chamber into the bore. Limited advan-r tages may be obtained by applying a tapered deposit to the bore alone. This procedure may be desirably used when the gun barrel does not integrally include a chamber. The distance to which the coating should vbe extended into the bore is not critical but itis imperative that` the coating does not extend throughout the entire length of the barrel. n a preferred modification, the coatingshould extend over about onethird of the length of the bore. The minimum length of coating of the bore should be such as to protect that portion of the bore immediately adjacent to the chamber which is subject to the .most severe erosive action. y J

Such coating is preferably produced by electroplating methods but it should be understood that the method of producing the coating ris immaterial to the practice' of the invention so long as a securely bonded coating of the described dimensions is produced.v

A gunl provided with one of the platings de'- scribed not only has greatly increased kresistance to corrosion and erosion but also has a substantial increase in muzzle velocity of the projectile as compared with an unplated gun of the same bore dimensions.Y The explanation `for-the substantial increase is not entirely clear but several factors are believed to contribute to its production. The most important factors` are believed strictiony is twofold;` rst, the available` clearance through'which the gases may blow by the progreater depth than necessary rfor the passage of the projectile along the unplated portion of the lands d. In effect, the projectile is sized by` the plated portion, then eased out intov the unplated portion of the bore by the taper 5a ofthe plating 5 and then more or less floats out through the remainder of the bore. The leakage of gases through the increased clearance between the projectile and the unplated portion of the bore is knot a serious factor in this portion of the bore since the gas pressure is substantially reduced. At any rate there would appear to be arsubstantial reduction of `irictional resistance to the movementof the projectile while traversing the unplated portion of the bore.Y There is also less friction'al resistance to the movement of the projectile in the plated portionv of the bore due to the Y lower coeicient of friction of the plating metal.

The slight constriction of the bore produced by the plating does not necessarily tend to increase projectile friction becausethe projectile is plastic under the applied pressure and upsets to ll the lbore and rining grooves.

It is toV be noted that the increase in velocity obtained by plating the rear portion of the bore is not only substantially greater than can be obtained by an unplated bore having the same dimensional constriction characteristics bu it is 40 v to depend on the slight constriction produced in a the bore by the coating. The eiect of this cony*with its muzzle end.

bore, said coating also substantially greater than that obtained by a bore plated its entire length.

Apart from' the retardation of corrosion and erosion 'which is inherent in a rplating of metal such as chromium, the life of the bore is further prolonged by the fact that the plating 5 protects f that portion of the lands 4 which does the initial work of swaging groovesA into the projectile, hence reducing wear on such portion.

I claim:

`l.` A gun barrel having a chamber and a bore anda metallic coating covering the chamber and the adjacent portion of the bore` said coating tapering to a negligible thickness Within the bore.

2. A gun barrel having a chamber and a bore and ametallic coating covering the chamberand the adjacent portion of the bore, said coating l having aVV uniform thickness throughout the chamber and tapering to a negligible thicknessy third of the bore., said plating tapering to a negligiblethickness.along the bore. c 5. A gun barrell having a chamber and a bore .andan electroplated deposit'oi' chromium "covering the chamber and the'adjacent portion of the bore Said. plating tapering to a negligible thing ness Within the bore. i f

6. A gun barrelhaving a' `chamber and a bore vand an electroplated deposit of chromium covering thev chamberand the adjacent portion of the bore, saidplating-'having a uniform thickness throughout the chamber and tapering to a 'negligihle thickness Within the bore.

' '7. A gun barrel having a chamber and a bore and af' tapered depth l `electroplated deposit of chromium appli'edto the chamber and the adjacentportion of the bore; said plating decreasing to a negligiblethickness within the bore.

8. A gun barrel having a corrosion-resistant, metallic coating. covering the breech 4end of the tapering to negligible thickness within the bore. f ,Y

9. A gun barrel having an electroplated deposit of chromium covering the breech end of the bore, said plating, vtapering to a negligible thickness within the bore.

l0. A gun barrel having achamber and a bore and a metallic coating covering a substantial portion of the bore which extends from a point adjacent the chamber to a point within the bore and being arranged whereby the bore isrelativeiy clonstrict'ed thruout the coated portion as contrasted fof the bore isrelativelyconstricted as contrasted with its Vunplated portion. 

